Quad-band planar frequency selective rasorber with T-A-A-T operating mode and high oblique incidence stability

A single layer frequency selective rasorber exhibiting dual-band transmissive and dual-band absorber characteristics is proposed. The dual-band absorber characteristics are achieved by two concentric circular rings with circular stubs on outer ring and circular slots in inner ring. The dual-band transmissive characteristics are achieved by two concentric circular ring apertures with additional quad diagonally circular rings. The absorber rings and transmissive aperture rings are separated by 0.8 mm thick FR-4 substrate. The Equivalent Circuit Model of the proposed Frequency Selective Rasorber (FSR) structure has been rigorously analyzed to understand the behavior of the quad-band transmissive and absorber characteristics. The measurement results demonstrated that a pass band with a minimal insertion loss of 0.21 dB can be achieved at 7.38 GHz and 10.80 GHz. The absorption rates of higher than 95% were obtained at 3.28 GHz and 16.618 GHz. The proposed quad-band FSR also verifies the polarization-insensitive behavior from 0° to 45°. Measurement results of proposed quad-band FSR prototype demonstrated superior agreement with simulated results and analytically ECM results. As compared to earlier reported geometries, novelty lies in its compact topology, higher angular stability, polarization insensitivity, and in band transmission response at desired range for filtering out unwanted signals in metrological satellites, surface ship radars, and various Radome applications.